ABSTRACT
The aim of this chapter is to introduce the basic physico-chemical concepts needed to understand the properties of nanostructured semiconductors, which are size- and shape-dependent. It will be shown that strong deviations from bulk values are found for the physico-chemical properties of the matter at the nanoscale, with the melting points which decrease with the decrease of the size and the energy gaps which increase, and with the onset of quantum confinement of electron and holes. Like other properties, the concentration of point defects also depends on size, and this should be accounted for at the nanoscale when considering processes which are driven by defects, like the doping processes.. Due to the experimental difficulties in applying methods used for bulk semiconductors at the nanoscale, most of the point defect properties should be determined with theoretical methods.
It will be shown, however, that thermodynamics might be applied with caution to small systems, since thermodynamics holds for macroscopic systems whose atomic density is at least close to the Avogadro number.
Surface defects play a critical role at the nanoscale, since the surface/volume ratio increases with the decrease of size, with the onset of intense light emission induced by surface defect states that covers emissions associated with core states.
It will be, eventually, shown that the small systems which will be dealt with in the next chapters, dots, nanocrystals, nanowires, represent the evolution of the miniaturization of semiconductor devices, the key of modern microelectronics.
